The present invention relates to a new and improved method of measuring errors in the truth of rotation of a gear.
Generally speaking, the method of measuring the rotational truth errors of gear teeth of a gear employs a measuring device having a feeler guide which is pivotable about a pivot axis disposed essentially parallel to the gear axis. The feeler guide guides a feeler which is pre-biased in the direction of the gear, cyclically engages into the gear teeth during such time as the gear rotates, and the feeler together with the feeler guide is pivoted about its pivot axis and forced or displaced back in relation to the feeler guide. Further, an electronic circuit determines, during each measuring cycle, the greatest degree of rearward displacement of the feeler in that it stores signals delivered by the feeler and compares the stored signals with one another.
With the present day high requirements placed upon the precision or accuracy of gear teeth of the most different types of gears, it is particularly important that cutting gears and other toothed tools, for fabricating such gear teeth, be machined extremely accurately. This requirement, among other things, makes it important that there be extremely accurately measured errors in the rotational truth of cutting gear teeth, so that they can be subsequently corrected as the need arises. Exact measurements of the rotational truth of gear teeth also must be carried out at standard gears which are not used as cutting gears and at gears which at the present time possess the greatest attainable diameters and number of teeth. Therefore, the need has existed for quite some time to measure the rotational truth of gears not only with utmost accuracy, but also with the least amount of time. The last-mentioned requirement means that it is desirable to be able to carry out the measurement at the highest possible rotational speed of the gear which is to be measured.
With all of the heretofore known equipment for performing the initially described method, there occurs between the feeler and the tooth flanks against which the feeler bears, due to the rotation of the gear, a rolling or generating movement upon which there is superimposed a sliding relative movement. The sliding relative movement is opposed by frictional forces which, within each measuring cycle, are appreciable, and often can periodically fluctuate. Consequently, the feeler is caused to oscillate. The amplitude of such oscillations, particularly at high rotational speeds of the gear, can assume an order of magnitude at which it is no longer immaterial during which oscillation phase there is obtained a measurement value for the largest rearward displacement of the feeler within each measuring cycle.
However, the heretofore methods do not take into account these factors in any way at all, nor do the measuring devices which have been proposed for the performance of such methods, and thus, reliable measurement results only can be obtained with such known methods and equipment, if at all, under the prerequisite that the measurements are carried out at low circumferential speeds of the gear teeth. Efforts to dampen the described oscillations in a manner such that the initially described method also can be employed for delivering sufficiently accurate measurements results, even during the measuring of gear teeth where the gears rotate at high circumferential or peripheral velocities, up to the present have not been very successful.